Shaft furnace charging installations of the BELL LESS TOP® type have found widespread use in industry during the last decades. An early example of such an installation is disclosed e.g. in U.S. Pat. No. 4,071,166. This installation minimizes escape of blast furnace gas from the furnace throat by operating one or more intermediate charge material storage hoppers in the manner of a sluice or airlock. To this effect, each hopper has an upper sealing valve and a lower sealing valve for sealing closure of the hopper inlet and outlet respectively. During filling of the hopper, the upper sealing valve is open whilst the lower sealing valve is closed. When material is charged from the hopper into the furnace, the lower sealing valve is open whilst the upper sealing valve is closed. U.S. Pat. No. 4,071,166 discloses a commonly used sealing valve arrangement with a flap-type valve, in which the shutter is tiltable about a single shaft. The axis of this shaft is arranged approximately in the plane of the valve seat. Since the shutter has to be completely removed from the material flow path in the open position, the arrangement according to U.S. Pat. No. 4,071,166 requires considerable space in the vertical direction, both inside the lower sealing valve housing and inside each intermediate storage hopper (see e.g. FIG. 1 of this patent). In other words, this valve arrangement requires a certain free height inside the sealing valve housing and limits the maximum filling height of the hoppers.
In order to reduce “lost” vertical constructional space, improved so-called dual-motion shutter-actuating devices have been proposed. U.S. Pat. No. 4,514,129 proposes such a dual-motion shutter-actuating device. This device is configured to tilt the valve about a first axis and to separately pivot the shutter together with its mounting arm about a second axis that is perpendicular to the first axis. This dual-motion shutter-actuating device allows moving the shutter into a higher parking position located laterally of and partially above the seat. The valve arrangement according to U.S. Pat. No. 4,514,129 thereby considerably reduces the required constructional height. U.S. Pat. No. 4,755,095 discloses a similar shutter-actuating device in an upper sealing valve arrangement, i.e. for sealing the inlet of the hopper. A drawback of these types of shutter-actuating devices however lies in that they have a number of articulated parts prone to wear and exposed to harsh conditions.
WO 2010/015721 A1 describes a further dual-motion lower sealing valve assembly for a shaft furnace charging installation comprising a lower sealing valve housing with a valve seat. The shutter is adapted to cooperate with the valve seat and operatively connected to a valve actuation mechanism, which can be supported by the top plate of the lower sealing valve housing, for moving the shutter into and out of sealing contact with the valve seat. In particular, the valve actuation mechanism comprises a turn-slide cylindrical joint supporting the shutter. The cylindrical joint has a substantially vertical joint axis according to which the joint allows translating the shutter up and down, e.g. in vertical direction, and in a plane perpendicular to which the joint allows swiveling the shutter, typically in a substantially horizontal plane. The turn-slide cylindrical joint comprises: a shaft, acting as output shaft of the joint, an intermediate hollow sleeve, in which the shaft is mounted, and an outer shell, supporting the sleeve and forming the fixed frame of the joint. The shaft is axially fixed and rotatable about the joint axis in the hollow sleeve. The sleeve is axially slidable along the joint axis in the outer shell that is fixed to the housing. The mechanism further comprises a first hydraulic cylinder for axial translation (sliding) and a second hydraulic cylinder for rotation (turning). The first cylinder has one side connected to the outer shell and the other side connected to the hollow sleeve, for axially translating the shaft with the sleeve along the joint axis relative to the shell. The second hydraulic cylinder has one side hinged to the sleeve and the other side hinged to the shaft in order to rotate the shaft relative to the intermediate sleeve about the joint axis. However, again, due to the fact that the translational movement is done in a dusty environment, the life time of the mechanism is shortened due to the fact that during actuation, dust may enter the seals and damage the sealing surfaces. A further disadvantage of this solution is the fact that particles falling on the shutter cannot fall down.
WO 2011/000966 A1 discloses a still further dual-motion shutter-actuating device is of the type configured to confer to the shutter a superposition of two rotations about substantially parallel and offset axes, i.e. offset axes having a relative orientation closer to parallel than to perpendicular. To this effect, the device comprises a primary tilting arm supported on a first tilting shaft, which is equipped with bearings to rotatably support the primary tilting arm on a stationary structure, typically either a lower sealing valve housing or on the shell of an intermediate storage hopper, in rotatable manner about an immobile first axis; a secondary tilting arm that carries the shutter and is supported on a second tilting shaft, which is equipped with bearings that rotatably support the secondary tilting arm on the primary tilting arm, in rotatable manner about a second axis that is essentially parallel to the first axis and moves with the secondary tilting arm; and a mechanism configured to impart rotation about the second axis to the secondary tilting arm at the same time as the primary tilting arm rotates about the first axis. In this solution, the first tilting shaft is configured as hollow sleeve shaft and the shutter-actuating device comprises a reference rod that extends through the first tilting shaft. This reference rod has a distal end portion to be connected to a stationary structure and a proximal end portion with a reference member, the mechanism having a driven side that is in engagement with the reference member. The main disadvantage of this solution is the number of movable parts, which render the device more costly in terms of manufacturing and assembling. Finally, the mechanism is to be operated inside a dusty environment although covered against dust.